The present invention relates to a method for improving the abrasion resistance of a spun-bonded nonwoven without substantially adversely affecting its hand or drape characteristics, by incorporating low melt binder fibers into the web during the laydown phase of the spun-bonded nonwoven production process. More specifically, improved abrasion resistance is achieved by intimately blending continuous binder fibers with the primary extruded fibers in a spun-bonded nonwoven web. Also encompassed within this invention is a spun-bonded nonwoven fabric having improved abrasion resistance and comprised of primary extruded fiber and low melt binder fiber such that the binder fiber comprises between about 1 and about 50 weight percent on weight of the spun-bonded nonwoven fabric.
Spun-bonded nonwoven production processes are well known in the textile arts and are described in various patents such as, for example, U.S. Pat. No. 4,692,618 to Dorschner, et al.; U.S. Pat. No. 4,340,563 to Appel, et al.; U.S. Pat. No. 3,338,992 to Kinney; U.S. Pat. No. 3,341,394 to Kinney; and U.S. Pat. No. 3,502,538 to Levy. Historically, the nonwoven webs produced from these processes have been produced for functional end-uses, such as for air filters, vehicle trunk linings, and roofing materials, with relatively low cost and little or no emphasis on the aesthetic properties of the nonwoven material.
More recently, developments in the area of spun-bonded fiber production have resulted in the creation of nonwoven fabrics with improved drape and hand characteristics (xe2x80x9chandxe2x80x9d typically describes the tactile qualities of a fabric such as softness, firmness, elasticity, etc.). For example, U.S. Pat. Nos. 5,899,785 and 5,970,583, both assigned to Firma Carl Freudenberg, describe a spun-bonded nonwoven lap of very fine continuous filament and the process for making such nonwoven lap using traditional spun-bonded nonwoven manufacturing techniques. Such references disclose, as important raw materials, spun-bonded composite, or multi-component, fibers that are longitudinally splittable by mechanical or chemical action into microdenier size individual fibers. However, many fabrics made from these processes typically lack the abrasion resistance required to enter new market segments.
Some attempts have been successfully made in the past to develop methods for imparting increased abrasion resistance to nonwoven webs, but they typically provide such improved abrasion resistance with a significant reduction in textile drape and hand characteristics. For example, a textile finishing process comprised of surface and/or back coating a nonwoven web produces a web having a protective layer over its fibers for improved abrasion resistance. Similarly, one or more polymeric layers, or one or more nonwoven layers, may be laminated to one or both sides of another nonwoven layer to create a composite material possessing increased abrasion resistance. Such a composite nonwoven material is described in U.S. Pat. No. 5,399,422 to Dijkema, et al.
Other methods for improving abrasion resistance in a nonwoven web while attempting to impart acceptable fabric hand and drape characteristics involve blending binder fibers with the primary fibers of the nonwoven web using needling and carding machines to produce carded needle-punched nonwovens, as described, for example, in U.S. Pat. No. 5,646,077 to Nobuhiro, et al. Typically, a binder fiber having a substantially lower melting point than the primary fibers is selected and intimately blended with the primary fibers prior to fiber carding and web consolidation. The consolidated web is then subjected to a thermal process to activate, or melt, the intimately blended binder fibers. The binder fibers typically comprise between about 2 and 15 weight percent of the nonwoven web, which facilitates the desired result of increased abrasion resistance without a subsequent reduction in textile drape and hand. This method, however, is limited to carded needle-punched nonwoven applications and has not yet been adapted for use in spun-bonded nonwovens partly due to the difference in the raw material, i.e. staple fiber is typically used in carding processes and continuous fiber is generated in a spun-bonding process.
A further method for improving abrasion resistance and attempting to achieve acceptable hand and drape characteristics in nonwoven fabrics has been to extrude binder fibers with the primary fibers of a spun-bonded nonwoven web. For example, U.S. Pat. No. 5,643,653 to Griesbach, et al., discloses a method for extruding multi-component fibers, wherein one component is a binder fiber and the second component is a primary (non-binder) fiber. Typically, the binder fiber has a lower melting point than the primary fiber. One disadvantage of this technique, however, is an increase in the complexity of the production process as a result of having a second fiber type to process through the drying/crystallizing, extrusion, and spinning steps involved in changing polymer pellet to continuous filament fiber. This increase in complexity will likely also lead to an undesirable increase in production cost. Furthermore, the spinning of the binder fiber requires a high level of processing care to secure the desired distribution of the binder fiber without adversely affecting the weight distribution of the primary fiber.
Thus, an efficient, cost effective method is needed for incorporating low melt binder fibers into a spun-bonded nonwoven web to achieve improved abrasion resistance without compromising the drape and hand of the resulting spun-bonded nonwoven fabric. The resulting fabric may be realized in a variety of end-use products such as, for example: (a) products historically comprised of multi-layer fabric and film nonwoven composites, (b) product historically manufactured from carded, needle-punched nonwovens, and (c) new products for markets such as apparel, upholstery, drapery, and napery.
In light of the foregoing discussion, it is one object of the current invention to achieve a method for producing a spun-bonded nonwoven web having improved abrasion resistance and comprised of primary extruded fiber and low melt binder fiber such that the low melt binder fiber comprises between about 1 and about 50 weight percent on weight of the spun-bonded nonwoven web. It is preferable that the introduction of the binder fibers to the spun-bonding process does not significantly interfere with polymer spinning or web laydown. Furthermore, it is preferable, during this introduction of the binder fibers, to intimately blend the binder fibers with the primary fibers of the web so that the resulting nonwoven fabric achieves improved abrasion resistance without adversely affecting either the fabric""s drape or hand characteristics, or the weight and thickness distribution of the fabric.
A further object of the current invention is to achieve a spun-bonded nonwoven fabric having improved abrasion resistance and comprised of primary extruded fiber and low melt binder fiber such that the low melt binder fiber comprises between about 1 and about 50 weight percent on weight of the spun-bonded nonwoven fabric. The fabric may be incorporated into a wide variety of end-use products, such as, for example, in articles of apparel, upholstery, napery, and drapery.
Another object of the current invention to achieve a method for producing a spun-bonded nonwoven web having improved aesthetic and/or performance characteristics and comprised of primary extruded fiber and secondary fiber or yarn such that the secondary fiber or yarn imparts the improved aesthetic and/or performance characteristics to the spun-bonded nonwoven web. The secondary fiber or yarn may be comprised, either partially or wholly, of binder fibers.
Yet a further object of the current invention is to achieve a spun-bonded nonwoven fabric having improved aesthetic and/or performance characteristics and comprised of primary extruded fiber and secondary fiber or yarn such that the secondary fiber or yarn imparts the improved aesthetic and/or performance characteristics to the spun-bonded nonwoven web. Herein again, the secondary fiber or yarn may be comprised, either partially or wholly, of binder fibers.
Other objects, advantages, and features of the current invention will occur to those skilled in the art. Thus, while the invention will be described and disclosed in connection with certain preferred embodiments and procedures, such embodiments and procedures are not intended to limit the scope of the current invention. Rather, it is intended that all such alternative embodiments, procedures, and modifications are included within the scope and spirit of the disclosed invention and limited only by the appended claims and their equivalents.